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Hello, I am trying to run the slope tool for an elevation raster that covers Sonoma and Napa counties in CA. I'd like to figure out the appropriate value to use for the z-factor. My elevation is measured in meters, and the coordinate system for the DEM is in degrees. The latitude in this area ranges from 38 to 39 degrees. Using the midpoint, 38.5, combined with the information on this Arc help page: http://resources.arcgis.com/en/help/main/10.1/index.html#//009z000000vm000000, I have determined that the appropriate z-factor is .0000115075. I did this using a simple linear interpolation for the 30- and 40-degree values referenced in the table contained in the link. Does this seem like a sound way to determine the appropriate z-factor? If not, could anyone suggest an alternative? Thanks, Dan
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07-30-2013
01:22 PM
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Hello, I'm trying to open some land cover data in Arc that has a .tar file extension. As far as I can tell from online documentation and forums, this extension means that the files are compressed and need to be extracted. Could anyone give me a pointer on how to go about extracting the data? Specifically, can i do this in Arc? I'm working in a university computer lab, so I can't download any extraction programs such as 7zip. Any help would be much appreciated. Data can be found here: http://www.fsl.orst.edu/pnwerc/wrb/dwnld_lulc1990.html, the first option being the one I'm trying to use. Best, Dan
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11-07-2012
09:22 AM
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Thank you. I manually set the cell size to the arbitrarily small value of "2" and it now works. Just as a note, setting the cell size to the minimum of the inputs did not alleviate the problem. Thanks again for the help.
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10-05-2012
09:36 AM
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I have a sample of 531 polygons (taxlots). I am trying to attribute the mean value of a precipitation raster to each polygon in my shapefile. However, when I run the Zonal Statistics as Table tool, I am only getting the desired values for 468 of the 531 polygons. The problem persists if I use Zonal Statistics (not as Table) instead. One thing I've noticed is that the polygons for which I am not getting values tend to be small (i.e. less than a half-acre). Has anyone else encountered this problem before? Namely, is there a threshold polygon size for Zonal Statistics, below which the tool will not work? I know that as a workaround I could convert the precipitation raster to a polygon and then clip and intersect it with my taxlots, but I don't want to go that route if it's not absolutely necessary. Any help would be greatly appreciated. Thanks!
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10-03-2012
01:25 PM
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